Structure with through hole, production method thereof, and liquid discharge head

ABSTRACT

A structure is constructed having a through hole in a substrate of silicon or the like by a decreased number of steps in production and with improved reliability. A silicon nitride film is formed in contact with an upper surface of a silicon oxide film at least on a portion of the substrate near the edge of a through hole, thereby improving step coverage of the silicon nitride film. The silicon oxide film and silicon nitride film function as a membrane during formation of the through hole by etching from the back side of the substrate.

This is a divisional application of application Ser. No. 10/270,650,filed on Oct. 16, 2002, now U.S. Pat. No. 7,018,020.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a structure with a through hole,comprised of a silicon (Si) semiconductor substrate and other elements,and a production method thereof and, more particularly, to a structuresuitably applied to thermal recording heads, ink jet recording heads,etc., used in printers and other devices, a production method thereof,and a liquid discharge head and apparatus having the structure.

2. Related Background Art

Structures with through hole(s) are used in various fields. For example,a structure with through hole(s) comprised of a silicon semiconductorsubstrate and other elements is used in ink jet recording heads whichare used in ink jet printers and other devices and adapted to dischargeink to implement recording. The following will describe a structure witha through hole, using an example of an ink jet recording head configuredto discharge ink by thermal energy.

The ink jet recording head utilizing thermal energy is configured toimpart thermal energy generated by a heating resistive element (heater),to a liquid to cause a bubbling phenomenon selectively in the liquid anddischarge an ink droplet from each discharge opening by the bubblingenergy. In the ink jet recording head of this type, in order to increasethe recording density (resolution), a number of fine heating resistorsare arranged on the silicon semiconductor substrate, discharge openingsare provided for the respective heating resistors so as to face theheating resistors, and drive and peripheral circuits for driving theheating resistors are also provided on the silicon semiconductorsubstrate.

FIG. 8 is a sectional view showing a configuration of such an ink jetrecording head.

As shown in FIG. 8, the ink jet recording head is constructed in astructure wherein a field oxide film (LOCOS oxide film) 101, a BPSG(boro-phospho silicate glass) layer 102 deposited by atmospheric CVD(chemical vapor deposition), and a silicon oxide film 103 deposited byplasma CVD are stacked on one principal surface of silicon substrate100, heating resistors (heaters) 110 are formed on the silicon oxidefilm 103, and a discharge opening 140 is provided so as to face eachheating resistor 110. In the drawing only one heating resistor 110 andone discharge opening 140 are depicted, but in fact, several hundredheating resistors and discharge openings are arranged in one ink jetrecording head. These heating resistors are arranged at predeterminedintervals (e.g., 40 μm) in the direction normal to the plane of thedrawing on the single silicon substrate 100.

In order to protect the heating resistors 110 and other elements, asilicon nitride film 104 is formed as a passivation layer by plasma CVD,over the whole of the aforementioned principal surface of the siliconsubstrate 100 including the regions on the heating resistors 110. Inportions corresponding to the heating resistors 110 along the surface ofthe silicon nitride film 104, tantalum (Ta) films 105 are formed asanti-cavitation layers in order to prevent deterioration of the siliconnitride film 104 due to the cavitation phenomenon caused by bubblesgenerated in the ink. The principal surface of the silicon substrate 100other than the principal surface on which the heating resistors 110 areformed, is covered by a thermal oxide film 106.

The discharge openings 140 are bored in a covering resin layer 130provided so as to cover the first aforementioned principal surface ofthe silicon substrate 100. A space is formed between the covering resinlayer 130 and, the silicon nitride film 104 and tantalum film 105, andthis space is a space filled with a liquid (ink) to be discharged fromthe discharge opening 140. This space will be called a liquid chamber150.

In the ink jet recording head having the structure described above, wheneach heating resistor 110 is energized to generate heat, the heatgenerates a bubble in the discharge liquid in the liquid chamber 150 andan action force of the bubble thus generated discharges a liquid dropletfrom the discharge opening 140. In order to implement continuousrecording, it is necessary to replenish the liquid chamber 150 with thedischarge liquid (ink) by the amount of liquid contained in the liquiddroplets discharged from the discharge opening 140. However, thedischarge openings 140 are located in the proximity of a recordingmedium, such as paper or the like, and the gap is also set to be smallbetween the discharge openings 140 and the heating resistors 110. It isthus difficult to supply the discharge liquid from the side of thesilicon substrate 100 where the heating resistors 110 are formed, intothe liquid chambers 150. For this reason, as illustrated, supplyopenings 120 are formed through the silicon substrate 100 and thedischarge liquid is allowed to flow through the supply openings 120 inthe direction indicated by the arrow in the drawing, whereby thedischarge liquid is supplied into the liquid chambers 150. The supplyopenings 120 are formed by selective etching of the silicon substrate100.

Meanwhile, the silicon substrate 100 normally has a thickness of severalhundred μm. If the silicon substrate 100 were etched from the principalsurface where the heating resistors 110 are formed, in order to form thesupply openings 120 by etching, the etching process would take a longtime even under setting of selective etching conditions and there wouldinevitably occur damage to each of the layers formed on the principalsurface and to the heating resistors 110. The supply openings 120 arethus formed by etching of the silicon substrate 100 from the principalsurface other than that on which the heating resistors 110 are formed.In that case, if an etchant flows to the side where the heatingresistors 110 are formed, upon penetration of the supply openings 120,it can cause damage to the heating resistors 110 and/or each of theother layers. Therefore, layers as etching stoppers are preliminarilyprovided at positions intended for formation of the supply openings 120on the principal surface of the silicon substrate 100 on which theheating resistors 110 are formed, whereby the etchant is prevented fromflowing to the side where the heating resistors 110 are formed.

In the example shown in FIG. 8, the field oxide film 101, BPSG layer102, and silicon oxide film 103 are not provided in the regions wherethe supply openings 120 are formed, and, instead thereof, siliconnitride films 107 formed by reduced pressure CVD are provided. Thesilicon nitride films 107 are patterned so as to be located only in theforming and surrounding regions of the supply openings 120, and endsthereof are formed so as to be interposed between the field oxide film101 and the BPSG film 102. In the forming region of each supply opening120, the silicon nitride film 107 is directly deposited on a thin oxidefilm 108 on the surface of the silicon substrate 100. The siliconnitride film 104 deposited by plasma CVD is also formed on the siliconnitride films 107 by reduced pressure CVD.

During the final stage of etching, the silicon nitride film 107 isexposed in the bottom of each supply opening 120 formed, as describedlater. If in this stage the silicon nitride film 107 and the siliconnitride film 104 crack or peel off from the silicon substrate 100, theetchant will leak to the side of the heating resistors 110, which is notpreferred. For this reason, as also described in Japanese PatentApplication Laid-Open No. 10-181032 (counterpart of U.S. Pat. No.6,143,190), the silicon nitride film 107 is formed by reduced pressureCVD, so that the internal stress of the silicon nitride film 107 becomesa tensile stress, which can prevent the occurrence of peeling or thelike.

Now, the structure of the heating resistor 110 will be described. FIG.9A is a schematic perspective view illustrating the structure of theheating resistor (heater), and FIG. 9B is a circuit diagram showing thepart including the heating resistor and a switching device for drivingit.

The heating resistor 110 is made in such a manner that a resistive layer111 made of an electrically resistive material, such as tantalum siliconnitride (TaSiN) or the like, and an aluminum (Al) layer 112 as anelectrode layer are formed in the same pattern, and a part of thealuminum layer 112 is removed so that only the resistive layer 111remains in that part of the heating resistor 110. The part where onlythe resistive layer 111 exists serves as a heat generating portion uponsupply of electricity (heating surface H). In the example illustrated,the resistive layer 111 and aluminum layer 112 are deposited in theorder named on the silicon oxide layer 103; thereafter, unnecessaryportions of the two layers are first removed by etching so as to leave aU-shaped pattern, and then only the aluminum layer 112 is furtherremoved in the part becoming the heating portion H, thereby completingthe heating resistor 110. Thereafter, the entire heating resistor 110 iscovered by the silicon nitride film 104 as a passivation layer.

A method of producing the ink jet recording head as described above willbe described next. In order to simplify the description, the followingdiscussion will exclude description of the thermal oxide film 106 formedon the side of the silicon substrate 100 other than the side on whichthe heating resistors 110 are formed, and FIGS. 10A to 10D and 11A to11C show only the structure of a supply opening 120 (the formingposition thereof) and its surroundings.

The production method of the ink jet recording head using the siliconsubstrate with through holes is described, for example, in JapanesePatent Application Laid-Open No. 10-181032. First, as shown in FIG. 10A,the field oxide film 101 is selectively formed, for example, in athickness of about 700 nm, on one principal surface of the siliconsubstrate 100. A thin oxide film 108 is formed in the region where nofield oxide film 101 is formed. Next, as shown in FIG. 10B, the oxidefilm 108 is removed at a portion corresponding to the forming positionof the supply opening 120 to expose the silicon surface and, as shown inFIG. 10C, a polysilicon layer 121 to become a sacrificial layer isfurther selectively formed at the exposed position of the siliconsurface, for example, in a thickness of 200 to 500 nm. At this time, thesilicon surface without the oxide film 108 completely surrounds thepolysilicon layer 121. Thereafter, as shown in FIG. 10D, the siliconnitride film 107 is selectively formed at and around the formingposition of the supply opening 120 by reduced pressure CVD. Thethickness of the silicon nitride film 107 is, for example, approximately200 to 300 nm.

Next, as shown in FIG. 11A, the BPSG layer 102 is formed, for example,in a thickness of 700 nm over the entire surface of the silicon nitridefilm 107 and the field oxide film 101 by atmospheric CVD, and thesilicon oxide film 103 is then formed, for example, in a thickness of1.4 μm over the entire surface of the BPSG layer 102 by plasma CVD. Thesurface of the silicon oxide film 103 is almost flat. Then, as shown inFIG. 11B, the silicon oxide film 103 and the BPSG layer 102 areselectively removed in a region that corresponds to the position wherethe supply opening 120 is to be formed but that is a little larger thanthe to-be-formed supply opening 120. At this time, the ends of theremoved part are located at positions where they are placed on thesilicon nitride film 107, and the field oxide film 101 also exists belowit.

Subsequently, the resistive layer 111 and aluminum layer 112 are formed,these are then patterned in the U-shaped pattern as described above, andthe aluminum layer 112 is further selectively removed from the positionto become the heating portion, thereby forming the heating resistor 110on the silicon oxide film 103. Thereafter, as shown in FIG. 1C, thesilicon nitride film 104 to become a passivation layer is formed, forexample, in a thickness of 800 nm over the entire surface, the tantalumfilm 105 as an anti-cavitation layer is selectively formed, and thesilicon substrate 100 at the supply opening forming position and thepolysilicon layer 121 as a sacrificial layer are removed by anisotropicetching from the side where no heating resistor 110 is formed on thesilicon substrate 100 (the lower side in the drawing), thereby formingthe supply opening 120. At this time, the silicon nitride film 107 linedwith the silicon nitride film 104 is exposed as a so-called membrane inthe bottom part of the supply opening 120. In the final stage of theetching, only this membrane serves to prevent the etchant from enteringthe heating resistor 110 side, so that keeping the membrane fromcracking or peeling off contributes to great improvement in the yield ofrecording heads.

Finally, the silicon nitride film 107 and the silicon nitride film 104are removed from the region located at the bottom surface of the supplyopening 120 by dry etching using a fluorine base or oxygen base gas.This completes the substrate for the recording head having the supplyopening 120 for supply of ink or the like as a through hole. Thereafter,the covering resin layer 130 and the discharge opening 140 are formed byknown methods.

Among the above steps, the patterning steps necessary for formation ofthe supply opening 120 (only those necessitating photomasks) include thestep of removing part of the oxide film 108 as shown in FIG. 10B, thestep of selectively providing the polysilicon layer 121 as shown in FIG.10C, the step of selectively providing the silicon nitride film 107 asshown in FIG. 10D, the step of removing the BPSG layer 102 and thesilicon oxide layer 103 by etching corresponding to the position of thesupply opening 120 as shown in FIG. 11B, and the step of forming thesupply opening 120 by etching of the silicon substrate 100 as shown inFIG. 1C.

On the other hand, the heating resistor 110 is connected at one end, forexample, to a power supply V_(H) of about +30 V and at the other end toa drain D of a MOS field effect transistor Ml as a switching device fordriving, as shown in FIG. 9B. A source S of the transistor M1 isgrounded and drive pulses are applied to a gate G of the transistor todrive the resistor. In the case where the drive circuit, including thetransistor Ml, and other peripheral circuits are formed on the siliconsubstrate 100, the BPSG layer 102 and the silicon oxide film 103 areformed so as to serve as interlayer dielectrics and the silicon nitridefilm 104 is formed so as to serve as a passivation layer. The fieldoxide film 101 is used for device isolation in the regions where thedrive and peripheral circuits are formed.

In the conventional structure, the reason why the silicon nitride film107 deposited by reduced pressure CVD is intentionally used as themembrane serving as an etching stopper during the formation of thesupply opening 120 by etching, is that the internal stress of this filmis a tensile stress. In contrast, the internal stress of the siliconoxide film 103 deposited by plasma CVD is a compressive stress. It hasbeen believed heretofore that it was necessary to maintain the tensionof the membrane through use of a film with a tensile stress as themembrane in order to avoid cracking or peeling off of the membraneduring etching. For this reason, the silicon nitride film 107 depositedby reduced pressure CVD has been used. Namely, it has been believed thatthe problem of cracking or peeling was unavoidable in the case of a filmwith a compressive stress.

In the case of the conventional production method of ink jet recordinghead described above, even if the method is arranged to simultaneouslyperform the step of providing the supply opening as a through hole inthe silicon substrate and the step of forming the heating resistor,drive circuit, and peripheral circuits on the silicon substrate, themethod requires at least five photomasks associated with only the stepof providing the supply opening, and the total number of photomasks usedis 17 or 18, including processing of other portions not here described.The steps are thus complex. Particularly, the silicon nitride film withthe tensile stress (the silicon nitride film deposited by reducedpressure CVD in the above example) needs to be provided as a membrane bypatterning and the silicon oxide film has to be patterned near theforming position of the through hole, which poses a problem that thenumber of manufacturing steps is large.

Since the conventional silicon nitride layer serving as a passivationlayer and as a membrane has a typical thickness of about 800 nm, themembrane region has a large compressive stress and the silicon nitridefilm having a tensile stress is needed for relaxation thereof. On theother hand, in the case of silicon nitride of this thickness, the heatgenerated by the heating resistor is transferred through this siliconnitride film to the discharge liquid, so that the utilization efficiencyof the heat is not satisfactory, thus posing a problem that thefrequency is limited in the case of executing repetitive discharges.

SUMMARY OF THE INVENTION

An object of the present invention is, therefore, to provide a structureand a production method thereof with a reduced number of steps, at lowcost, and with high reliability.

Another object of the present invention is to provide a structure withan excellent through hole and a production method thereof.

Still another object of the present invention is to provide a liquiddischarge head and a liquid discharge apparatus using such a structure.

The present invention accomplishes at least one of these.

In the present invention, a silicon nitride film is provided on an uppersurface of a silicon oxide film and the stack structure of the siliconoxide film and the silicon nitride film is also used in that state as amembrane against etching for formation of a through hole, even at theforming position of the through hole. The silicon oxide film is used,for example, as an interlayer dielectric or the like and normally has analmost flat upper surface. Therefore, the silicon nitride film formedthereon is also resistant to formation of a step, whereby the membraneis prevented from cracking or the like during the formation of thethrough hole by etching. The silicon oxide film stated herein can bechosen from among SiO_(x) films formed by plasma CVD, silicon oxidescontaining impurities, such as PSG, BSG, and BPSG films, and so on.

Specifically, a structure according to the present invention comprises asemiconductor substrate, a silicon oxide film and a silicon nitride filmprovided on a first principal surface of the semiconductor substrate,and a through hole penetrating the semiconductor substrate, the siliconoxide film, and the silicon nitride film, wherein the silicon nitridefilm is formed in contact with an upper surface of the silicon oxidefilm, at least at a side portion of the through hole.

A production method of a structure according to the present invention isa method of producing a structure comprising a semiconductor substrate,a silicon oxide film and a silicon nitride film provided on a firstprincipal surface of the semiconductor substrate, and a through holepenetrating the semiconductor substrate, the silicon oxide film, and thesilicon nitride film, the method comprising: forming a sacrificial layeron the first principal surface of the semiconductor substrate at aposition corresponding to a forming position of the through hole;forming the silicon oxide film so as to cover the whole of thesacrificial layer and the first principal surface; forming the siliconnitride film on an upper surface of the silicon oxide film; thereafter,etching the semiconductor substrate from a second principal surface sideof the semiconductor substrate to remove the sacrificial layer; andetching the silicon oxide film and the silicon nitride film to form thethrough hole.

The present invention as described above obviates the need for provisionof a silicon nitride film formed so as to have a tensile stress byreduced pressure CVD only for the purpose of serving as a membrane.

In the present invention, it is preferable that the semiconductorsubstrate be a silicon substrate, and it is preferable that a circuitelement be provided on the first principal surface of the siliconsubstrate. The circuit element herein is, for example, a MOS fieldeffect transistor formed on the first principal surface by an ordinarysemiconductor production process. In the case where the circuit elementis provided, the sacrificial layer can be made of the same material asthe gate electrode or the source-drain electrodes of the circuit elementand simultaneously in the step of forming the gate electrode or thesource-drain electrodes.

The structure described above is also suitably applicable as a substratefor a recording head. Such a substrate for a recording head is arecording head substrate comprising a semiconductor substrate, a siliconoxide film and a silicon nitride film provided on a first principalsurface of the semiconductor substrate, a heating resistor interposedbetween the silicon oxide film and the silicon nitride film, and asupply opening penetrating the semiconductor substrate, the siliconoxide film, and the silicon nitride film and adapted to supply a liquid,wherein the silicon nitride film is formed in contact with an uppersurface of the silicon oxide film, at least at a side portion of thesupply opening. In this case, it is particularly preferable that thesemiconductor substrate be a silicon substrate and that a circuitelement for driving the heating resistor be provided on the firstprincipal surface.

A liquid discharge apparatus according to an embodiment of the presentinvention comprises a liquid discharge head, and a container foraccommodating the liquid supplied through the supply opening.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view showing a structure as anembodiment of the present invention, which is used as a substrate for anink jet recording head;

FIGS. 2A, 2B and 2C are schematic sectional views showing productionsteps of the structure shown in FIG. 1;

FIGS. 3A and 3B are schematic sectional views showing production stepsof the structure shown in FIG. 1;

FIG. 4 is a schematic sectional view showing a structure as anotherembodiment of the present invention, which is used as a substrate for anink jet recording head;

FIGS. 5A, 5B and 5C are schematic sectional views showing productionsteps of the structure shown in FIG. 4;

FIGS. 6A and 6B are schematic sectional views showing production stepsof the structure shown in FIG. 4;

FIG. 7 is a perspective view showing an ink jet recording apparatus;

FIG. 8 is a schematic sectional view showing a configuration of aconventional ink jet recording head;

FIG. 9A is a perspective view showing a heating resistor, and FIG. 9B acircuit diagram showing a circuit including a heating resistor and aswitching device (MOS field effect transistor) for driving it;

FIGS. 10A, 10B, 10C and 10D are sectional views showing production stepsof the ink jet recording head shown in FIG. 8; and

FIGS. 11A, 11B and 11C are sectional views showing production steps ofthe ink jet recording head shown in FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will be describedbelow with reference to the drawings.

FIG. 1 is a schematic sectional view showing a structure as a preferredembodiment of the present invention. In FIG. 1, the elements denoted bythe same reference symbols as those in FIGS. 8, 10A to 10D, and 11A to11C have functions similar to those in FIGS. 8, 10A to 10D, and 11A to11C.

The structure shown in FIG. 1 is configured as a substrate for an inkjet recording head as a liquid discharge head or a liquid dischargeapparatus and is different from the aforementioned structure shown inFIGS. 8, 10A to 10D, and 11A to 11C in that the silicon nitride film 104is formed in contact with the upper surface of the silicon oxide film103 at the side portion of the through hole. Specifically, it isdifferent in detail in that, without provision of the silicon nitridefilm formed by reduced pressure CVD, the membrane used during theformation of the supply opening is constructed of the BPSG layer 102deposited by atmospheric CVD, the silicon oxide film 103 deposited byplasma CVD, and the silicon nitride film 104 deposited by plasma CVDwhich also functions as a passivation layer. The internal stress of thesilicon nitride film 104 is preferably a compressive stress of not morethan 3×10⁸ Pa. In the structure shown in FIGS. 8, 10A to 10D, and 11A to11C, the BPSG layer 102 and the silicon oxide film 103 were removed inthe size greater than the diameter of the supply opening 120, whereas inthe structure shown in FIG. 1, the BPSG layer 102, silicon oxide film103, and silicon nitride film 104 are removed in the size approximatelyequal to that of the supply opening 120. At the edge part of the supplyopening 120, the BPSG layer 102 is in direct contact with the siliconsubstrate 100, without intervention of the oxide film. Although notillustrated herein, drive and peripheral circuits for driving eachheating resistor are monolithically integrated on the silicon substrate100 as occasion demands. The following will describe as an example thestructure with the drive and peripheral circuits integrated.

A production method of this structure will be described below withreference to FIGS. 2A to 2C, 3A and 3B. FIGS. 2A to 2C, 3A and 3B showonly the vicinity of the position where a supply opening 120 is to beformed, and are drawn without illustration of the forming region of theheating resistor.

First, as shown in FIG. 2A, the field oxide film 101 is selectivelyformed, for example, in a thickness of about 700 nm on one principalsurface of the silicon substrate 100, for example, by thermal oxidation.The thin oxide film 108 is formed in the region without the field oxidefilm 101. Next, as shown in FIG. 2B, the oxide film 108 is removed at aposition corresponding to the forming position of the supply opening 120to expose the silicon surface there and, as shown in FIG. 2C, thepolysilicon layer 121 as a sacrificial layer is further selectivelyformed, for example, in a thickness of 200 to 500 nm, at the exposedposition of the silicon surface, for example, by reduced pressure CVDand reactive ion etching. At this time, a portion of the silicon surfacewithout the oxide film 108 completely surrounds the polysilicon layer121. Before completion of the stage shown in FIG. 2C, the steps offorming a gate insulating film and gate electrodes are finished in theforming region of the drive and peripheral circuits. Here thepolysilicon layer 121 is preferably formed in the same steps as the filmforming step and etching step of the gate electrodes of the MOStransistors constituting the drive and peripheral circuits, becausethere is no need for provision of a mask dedicated for the sacrificiallayer.

The process is also arranged to complete a step of implantation ofimpurity ions into the source/drain regions thereafter.

Then as shown in FIG. 3A, the BPSG layer 102 is formed, for example, ina thickness of 700 nm over the entire surface by atmospheric CVD, and,in the drive and peripheral circuits, contact holes are formed byetching, a conductor layer of aluminum or the like is formed for thesource and drain electrodes, and a wiring pattern is formed by dryetching with a chlorine base gas.

Then the silicon oxide film 103 is formed, for example, in a thicknessof 1.4 μm over the entire surface on the BPSG layer 102 by plasma CVD.In the drive and peripheral circuits, the silicon oxide film 103 servesas an interlayer dielectric covering the conductor layer, and throughholes are formed therein by reactive ion etching.

Although not shown herein, the heating resistors are also formed in muchthe same manner as in the case of the conventional technology, and areconnected through the through holes to the drive circuit.

Thereafter, as shown FIG. 3A, the silicon nitride film 104 to become apassivation layer is formed, for example, in a thickness of 300 nm overthe entire surface on the silicon oxide film 103, the heating resistors,and so on. Since in the vicinity of the forming position of the supplyopening 120 the BPSG layer 102 and the silicon oxide film 103 are leftwithout being etched, below the silicon nitride film 104, the siliconnitride film 104 is formed as an extremely flat film. After that, atantalum film (not shown) as an anti-cavitation layer is selectivelyformed. Then, as shown in FIG. 3B, an anti-etching mask (not shown) isformed on the back surface of the substrate, and the silicon substrate100 at the forming position of each supply opening and the polysiliconlayer 121 as a sacrificial layer are removed from the lower side of thesilicon substrate 100 in the drawing by anisotropic etching using anetchant such as TMAH (tetramethylammoniumhydroxide) or the like, therebyforming the supply openings 120. At this time, the membrane of the stackconsisting of the BPSG layer 102, silicon oxide film 103, and siliconnitride film 104 is exposed in the bottom part of each supply opening120.

Finally, the BPSG layer 102, silicon oxide film 103, and silicon nitridefilm 104 located on the bottom surface of the supply opening 120 areremoved from the back surface of the substrate by dry etching using afluorine base or oxygen base gas. This results in completing therecording head substrate having the supply openings 120 for supply ofink or the like as through holes. The etching step herein may be wetetching for removing the silicon oxide film 103. Thereafter, thecovering resin layer 130 and the discharge openings 140 are formed byknown methods, thereby completing the ink jet recording head having theabove-stated structure as a substrate for a recording head.

Various insulating layers necessary for the circuit elements such astransistors in the drive and peripheral circuits are formed inconjunction with the forming steps of the field oxide film 101, BPSGlayer 102, and silicon oxide film 103, as described above.

In the case where the structure described above is formed as a substratefor the ink jet recording head, the patterning steps associated withonly the formation of the supply openings 120 (only the stepsnecessitating photomasks) include the step of removing part of the oxidefilm 108 as shown in FIG. 2B, the step of selectively providing thepolysilicon layer 121 as shown in FIG. 2C, and the step of forming thesupply openings 120 by etching of the silicon substrate 100 as shown inFIG. 3B. The number of steps is two less than the number of steps in theconventional method shown in FIGS. 10A to 10D and 11A to 11C.Furthermore, if the forming step of the polysilicon layer 121 as asacrificial layer is carried out simultaneously in the step of formingthe gate electrodes of the MOS transistors, the number of steps isfurther reduced by one. Accordingly, the method of the presentembodiment can reduce the total number of necessary photomasks by two orthree, compared with the conventional methods. Since the structure ofthe present embodiment permits the silicon nitride film to be formed ina smaller thickness than the silicon nitride films used heretofore, itis feasible to further increase the thermal efficiency as compared withthe conventional structures and, at the same time, decrease thecompressive stress of the film stack constituting the membrane region,which obviates the need for the step of forming the silicon nitride filmso as to have a tensile stress.

FIG. 4 is a schematic sectional view showing a structure as anotherembodiment of the present invention. The structure shown in FIG. 4 isconstructed as a substrate for an ink jet recording head and is similarto the aforementioned structure shown in FIG. 1, but is differenttherefrom in that at the edge part of the supply opening 120, the BPSGlayer 102 is not in direct contact with the silicon substrate and,instead thereof, the silicon oxide film 103 is in direct contact withthe silicon substrate 100, without intervention of an oxide film.

A production method of this structure will be described below withreference to FIGS. 5A to 5C, 6A and 6B. FIGS. 5A to 5C, 6A and 6B showonly the vicinity of the position where a supply opening 120 is to beformed, and are drawn without the illustration of the forming region ofthe heating resistor.

First, as shown in FIG. 5A, the field oxide film 101 is selectivelyformed, for example, in a thickness of about 700 nm on one principalsurface of the silicon substrate 100. The thin oxide film 108 is formedin the region where no field oxide film 101 is formed. This oxide film108 is preferably arranged to function as a gate oxide film in the driveand peripheral circuits, because the number of steps can be reducedthereby. Thereafter, the gate electrodes are formed in the region of thedrive and peripheral circuits, and impurity ions are injected into thesource/drain regions. Thereafter, as shown in FIG. 5B, the BPSG layer102 is formed, for example, in a thickness of 700 nm over the entiresurface by atmospheric CVD, and then the BPSG layer 102 and oxide film108 are removed by etching to expose the silicon surface, in positionscorresponding to the positions where the supply openings 120 are to beformed, simultaneously in the step of forming the contact holes in thedrive and peripheral circuits. This step requires no mask dedicated onlyfor exposing the silicon surface in the supply opening portions.Furthermore, as shown in FIG. 5C, a film of aluminum (Al) containingcopper (Cu) or silicon (Si) is selectively deposited and etched at theexposed positions of the silicon surface to form a sacrificial layer 122of aluminum, for example, in a thickness of 400 to 800 nm,simultaneously in the step of forming the source and drain electrodes inthe drive and peripheral circuits. When this layer of aluminumcontaining copper or silicon is used as an electrode contact layer inthe drive and peripheral circuits, there is no need for provision of amask dedicated only for the formation of the sacrificial layer in thesupply opening portions. At this time, the silicon surface without theoxide film 108 completely surrounds the sacrificial layer 122. It ispreferable to use a metal such as aluminum or the like as thesacrificial layer, as in the present embodiment, rather than usingpoly-Si as the sacrificial layer. The reason for this is as follows. Ametal such as aluminum or the like can also be used readily as a layerof the peripheral circuits, whereas in the case of poly-Si, it would benecessary to employ a configuration doped with impurities, dependingupon the conditions, in order to also use it for the peripheralcircuits. When such poly-Si is used as the sacrificial layer, etchingrates can decrease.

Then, as shown in FIG. 6A, the silicon oxide film 103 is formed, forexample, in a thickness of 1.4 μm over the entire surface by plasma CVD.Thereafter, though not shown herein, the heating resistors are formedtogether with wiring plugs and wiring layers for wiring, in much thesame manner as in the case of the conventional technology. Furthermore,as shown in FIG. 6A, the silicon nitride film 104 to become apassivation film is formed, for example, in a thickness of 300 nm overthe entire surface by plasma CVD, and the tantalum film (not shown) asan anti-cavitation layer is further selectively formed.

Then, as shown in FIG. 6B, the silicon substrate 100 at each supplyopening forming position and the sacrificial layer 122 are removed byanisotropic etching from the lower side of the silicon substrate 100 inthe drawing, to form the supply openings 120. At this time, the membraneconsisting of silicon oxide film 103 and silicon nitride film 104 isexposed in the bottom part of each supply opening 120.

Finally, the silicon oxide film 103 and silicon nitride film 104 areremoved from the bottom surface of each supply opening 120 by dryetching using a fluorine base or oxygen base gas. The etching stepherein may be wet etching for removing the silicon oxide film 103. Thisresults in completing the substrate for the recording head having thesupply openings 120 for supply of ink or the like as through holes.Thereafter, the covering resin layer 130 and discharge openings 140 areformed by known methods, thereby completing the ink jet recording headusing the structure as a substrate for the recording head.

In the case where the structure described above is formed as a substratefor an ink jet recording head, since some patterning steps necessary forthe formation of the supply openings are carried out in the same stepsas the contact hole forming step, the electrode forming step, and thethrough hole forming step necessary for the formation of the drive andperipheral circuits, the patterning step associated with the formationof the supply openings 120 (the only step necessitating a photomask)includes only the step of forming the supply openings 120 by etching ofthe silicon substrate 100. This amounts to four fewer steps than in theconventional method shown in FIGS. 10A to 10D and 11A to 11C.Accordingly, the method of the present embodiment can decrease the totalnumber of necessary photomasks by four, compared to the conventionalmethod. Since the structure of the present embodiment permits thesilicon nitride film to be formed in a smaller thickness than in theconventional structures, it is feasible to further increase the thermalefficiency, as compared with the conventional structures, and, at thesame time, decrease the compressive stress of the film stackconstituting the membrane region, which can obviate the necessity of thestep of forming the silicon nitride film so as to have a tensile stress.In addition, the configuration of the present embodiment is preferablein that the durability against ink is further enhanced, because the BPSGfilm is not exposed at the edge part of the supply openings.

In each of the above embodiments, when the heating resistors aremonolithically integrated together with the devices such as thetransistors forming the drive and peripheral circuits, some steps can beperformed in common with steps for the formation of the supply openings,which can greatly simplify the production process.

The following will describe a liquid discharge apparatus according tothe present invention, i.e., an ink jet recording apparatus providedwith the ink jet recording head as described above. FIG. 7 is aschematic perspective view showing a configuration of such an ink jetrecording apparatus. The apparatus herein is constructed using a headcartridge 51 of the structure in which the ink jet recording head 52 isintegrated with an ink tank 53 as a container for accommodating ink.

The head cartridge 51 is replaceably (detachably) mounted on a carriage54. The carriage 54 moves back and forth in the directions X, Y (themain scanning directions) in the drawing, along a carriage drive shaft55 and a guide shaft 56, through rotation of the carriage drive shaft(lead screw) 55. Namely, a spiral groove 57 is formed in the carriagedrive shaft 55, and the carriage 54 is provided with a pin (not shown)engaging the spiral groove 57. With rotation of the carriage drive shaft55, the carriage 54 moves in parallel along the spiral groove 57. Thehead cartridge 51 is fixed at a predetermined position relative to thecarriage 54 by positioning means, and is electrically connected throughcontacts to a flexible cable connecting the carriage 54 with a controlcircuit on the main body side of the recording apparatus.

In FIG. 7, opposite the carriage 54 and within the moving range of thecarriage 54, a conveying roller 59 for holding and feeding (conveying) arecording medium 58 is rotatably supported in parallel with the carriagedrive shaft 55. In the illustrated example, the conveying roller 59 alsoserves as a platen (platen roller). The conveying roller 59 is rotatablydriven by a conveying motor 60. The recording medium 58 is pressedagainst the conveying roller (platen roller) 59 throughout the moving(main scanning) direction of the carriage 54 by a sheet presser 61, atthe recording position.

A driving motor 62 is mounted on the main body side of the recordingapparatus, and the carriage drive shaft (lead screw) 55 is rotatablydriven thereby through driving force transmission gears 63, 64. Thecarriage 54 is caused to move in the X or Y directions by rotating thecarriage drive shaft 55 forward or backward through forward or backwardrotation of the driving motor 62.

A home position of the carriage 54 is set at a predetermined position (aposition on the left side in the drawing) outside of the recordingregion and within the moving range of the carriage 54. A photocoupler 65is located in the vicinity of the home position. When the carriage 54arrives at the home position, the photocoupler 65 detects entry of alever 66 disposed on the carriage 54, thereby detecting the arrival ofthe carriage 54 at the home position. Namely, the photocoupler 65 isused as a detecting means (sensor) for controlling various operations ofthe recording apparatus, including an operation of switching therotating direction of the driving motor 62 so as to reverse the carriagemoving direction upon the arrival of the recording head 52 at the homeposition, an operation of starting a recovery operation in order toeliminate or prevent plugging of the discharge openings of the recordinghead 52, and so on.

A cap 68 for covering (hermetically closing) the discharge openingsurface of the recording head 52 in the head cartridge 51 is provided atthe home position. The cap 68 is supported by a cap holder 69 so as tobe movable in directions in which it is brought into close fit with thedischarge opening surface and in which it is retracted away therefrom. Ablade (cleaning member) 70 for wiping (cleaning) the discharge openingsurface is located between the cap 68 and the recording region. Thisblade 70 is held by a blade holder 72 supported by a body support plate71 so as to be movable between an advanced position where it can wipethe discharge opening surface and a retracted position where it is outof contact with the discharge opening surface.

In addition to the form of the blade 70, the cleaning means for thedischarge opening surface can take any one of various forms as long asit is a member capable of removing foreign particles. The operationsincluding the capping of the discharge opening surface, the cleaning ofthe discharge opening surface, etc. are carried out with the carriage 54being stationary or in motion at the corresponding position(s) and atpredetermined timings through the action of the spiral groove 57 of thecarriage drive shaft 55 when the carriage 54 comes to the region on thehome position side.

The above discussion described the embodiments of the present inventionas examples in which a substrate for an ink jet recording head wasformed, but it is noted that the present invention is by no meansintended to be limited to such examples and is generally applicable toformation of a through hole in a structure such as a silicon substrateor the like. For example, it is also applicable to the production ofso-called micromachines or the like.

1. A method of producing a liquid discharge head comprising asemiconductor substrate, a silicon oxide film and a silicon nitridefilm, wherein the silicon oxide film and the silicon nitride film aredisposed on a first principal surface of the semiconductor substrate,and a through hole is formed to penetrate the semiconductor substrate,the silicon oxide film, and the silicon nitride film, said methodcomprising: forming a sacrificial layer on the first principal surfaceof the semiconductor substrate, at a position corresponding to a formingposition of the through hole; forming the silicon oxide film so as tocover the sacrificial layer and the whole of the first principal surfaceof the semiconductor substrate; forming the silicon nitride film on thesilicon oxide film; and thereafter, etching the semiconductor substratefrom a second principal surface side of the semiconductor substrate soas to remove the sacrificial layer, and etching the silicon oxide filmand the silicon nitride film so as to form the through hole.
 2. Themethod according to claim 1, wherein the silicon nitride film is formedby a plasma CVD process.
 3. The method according to claim 1, furthercomprising forming a circuit element on the first principal surface ofthe semiconductor substrate, wherein the semiconductor substratecomprises a silicon substrate and the circuit element comprises atransistor.
 4. The method according to claim 3, wherein the sacrificiallayer is formed together with and is formed of the same material asgate, source and drain electrodes of the transistor.
 5. A liquiddischarge head produced according to claim 1, wherein the through holeis used as a supply port for a liquid.
 6. A liquid discharge apparatuscomprising a liquid discharge head produced according to claim 1, and acontainer storing a liquid for supplying through the through hole as asupply port.
 7. A method of producing a structure comprising asemiconductor substrate, a circuit element comprising a transistordisposed on a first principal surface of the semiconductor substrate, asilicon oxide film, and a silicon nitride film, wherein the siliconoxide film and the silicon nitride film are disposed on a firstprincipal surface of the semiconductor substrate, and a through hole isformed to penetrate the semiconductor substrate, the silicon oxide film,and the silicon nitride film, said method comprising: forming asacrificial layer on the first principal surface of the semiconductorsubstrate, at a position corresponding to a forming position of thethrough hole; forming the silicon oxide film so as to cover thesacrificial layer and the whole of the first principal surface of thesemiconductor substrate; and forming the silicon nitride film on thesilicon oxide film; thereafter, etching the semiconductor substrate froma second principal surface side of the semiconductor substrate so as toremove the sacrificial layer, and etching the silicon oxide film and thesilicon nitride film so as to form the through hole.
 8. The methodaccording to claim 7, wherein the sacrificial layer is formed togetherwith and is formed of the same material as gate, source and drainelectrodes of the transistor.
 9. A method of producing a structurecomprising a semiconductor substrate, a silicon oxide film, and asilicon nitride film, wherein the silicon oxide film and the siliconnitride film are disposed on a first principal surface of thesemiconductor substrate, and a through hole is formed to penetrate thesemiconductor substrate, the silicon oxide film, and the silicon nitridefilm, said method comprising: forming a field oxidization film on thefirst principal surface of the semiconductor substrate; forming asacrificial layer on the first principal surface of the semiconductorsubstrate at a position corresponding to a forming position of thethrough hole in a region partitioned by the field oxidization film;forming a BPSG film so as to cover at least the field oxidization film;forming the silicon oxide film so as to cover the sacrificial layer andthe BPSG film; forming the silicon nitride film on the silicon oxidefilm; and thereafter, etching the semiconductor substrate from a secondprincipal surface side of the semiconductor substrate so as to removethe sacrificial layer, and etching the silicon oxide film and thesilicon nitride film so as to form the through hole.